[Arny Krueger]

"The Phantom" wrote in message
...
On Tue, 21 Aug 2007 07:35:03 -0400, "Arny Krueger"
wrote:


"Eeyore" wrote in message
...


Arny Krueger wrote:

"Eeyore" wrote:
John Byrns wrote:

A Bel or 10 dB seems like an awfully large loss for "a standard
telephone line over the distance of one mile, at 1kHz", is this
really
correct?

I suggest you consider the DC resistance of a mile (and a mile back)
of
thin wire.

Telephone wire in the US is usually 24 or 26 gauge. Taking the worst
case:

26 gauge - 40 ohms/1000 feet = 211 ohms/mile, presuming the return
path
is
a low resistance ground.

The reurn is a length of the same wire.

Yes, the line is usually balanced. So about double the loss to about 5
dB/mile.

Presuming the load is 600 ohms, loss is 0.739 or 2.6 dB.

The load is rarely 600 ohms AIUI.

Do you think it is higher or lower than 600 ohms?


An example is given on page 69 of the book "Transmission Circuits for
Telephonic Communication".

I quote:

"In order to get a clearer idea of what is meant by transformer and
transition losses as well as to get a more concrete idea of their order of
magnitude, let us consider the case of an e.m.f. E acting through a
sending
end impedance Z1 of 240 - j123 ohms and connected to a receiving end
impedance Z2 of 623 - j350 ohms."

Make of it what you will.

The magnitude of the source is 269 ohms.

The magnitude of the load is 714 ohms

On page 70 and 71, they discuss a test set for comparing transmitters
(carbon microphones, I think). The circuit simulates the sending end
circuitry of a telephone and has 8 miles of cable as well as some
transformers and induction coils (as they called them; they were just
inductors). The impedance driving the telephone line wasn't just the
impedance of the microphone; it was modified by the additional circuitry.
They then say:

"In this particular circuit the 800 cycle impedance at the transmitter
terminals is approximately 307 - j74 ohms. It is, therefore, seen that
with present commercial types of transmitters, ranging between 30 and 150
ohms in resistance, this circuit will discriminate in favor of the
transmitter having the higher resistance."
-------------------------------------------------------------------------


The magnitude of the source is 315 ohms.


On page 150, they say:

"For example, the 800-cycle iterative impedance of a non-loaded No. 19
gauge cable circuit is approximately 500 @ 45 degrees, and that of a
non-loaded open wire line is about 700 @ 14 degrees ohms."

500 ohms and 700 ohms are impedance magnitudes as is.

Thanks.

[John Byrns]

In article ,
"Arny Krueger" wrote:

"The Phantom" wrote in message
...
On Tue, 21 Aug 2007 07:35:03 -0400, "Arny Krueger"
wrote:


"Eeyore" wrote in message
...


Arny Krueger wrote:

"Eeyore" wrote:
John Byrns wrote:

A Bel or 10 dB seems like an awfully large loss for "a standard
telephone line over the distance of one mile, at 1kHz", is this
really
correct?

I suggest you consider the DC resistance of a mile (and a mile back)
of
thin wire.

Telephone wire in the US is usually 24 or 26 gauge. Taking the worst
case:

26 gauge - 40 ohms/1000 feet = 211 ohms/mile, presuming the return
path
is
a low resistance ground.

The reurn is a length of the same wire.

Yes, the line is usually balanced. So about double the loss to about 5
dB/mile.

Presuming the load is 600 ohms, loss is 0.739 or 2.6 dB.

The load is rarely 600 ohms AIUI.

Do you think it is higher or lower than 600 ohms?


An example is given on page 69 of the book "Transmission Circuits for
Telephonic Communication".

I quote:

"In order to get a clearer idea of what is meant by transformer and
transition losses as well as to get a more concrete idea of their order of
magnitude, let us consider the case of an e.m.f. E acting through a
sending
end impedance Z1 of 240 - j123 ohms and connected to a receiving end
impedance Z2 of 623 - j350 ohms."

Make of it what you will.

The magnitude of the source is 269 ohms.

The magnitude of the load is 714 ohms

On page 70 and 71, they discuss a test set for comparing transmitters
(carbon microphones, I think). The circuit simulates the sending end
circuitry of a telephone and has 8 miles of cable as well as some
transformers and induction coils (as they called them; they were just
inductors). The impedance driving the telephone line wasn't just the
impedance of the microphone; it was modified by the additional circuitry.
They then say:

"In this particular circuit the 800 cycle impedance at the transmitter
terminals is approximately 307 - j74 ohms. It is, therefore, seen that
with present commercial types of transmitters, ranging between 30 and 150
ohms in resistance, this circuit will discriminate in favor of the
transmitter having the higher resistance."
-------------------------------------------------------------------------


The magnitude of the source is 315 ohms.


On page 150, they say:

"For example, the 800-cycle iterative impedance of a non-loaded No. 19
gauge cable circuit is approximately 500 @ 45 degrees, and that of a
non-loaded open wire line is about 700 @ 14 degrees ohms."

500 ohms and 700 ohms are impedance magnitudes as is.

Why do you focus on the magnitude of the impedance to the exclusion of
the phase angle? According to the old telephone book I have the phase
angle of the impedance is also important in telephonic transmission.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Arny Krueger]

"John Byrns" wrote in message
...
In article ,
"Arny Krueger" wrote:

"The Phantom" wrote in message
...
On Tue, 21 Aug 2007 07:35:03 -0400, "Arny Krueger"
wrote:


"Eeyore" wrote in message
...


Arny Krueger wrote:

"Eeyore" wrote:
John Byrns wrote:

A Bel or 10 dB seems like an awfully large loss for "a standard
telephone line over the distance of one mile, at 1kHz", is this
really
correct?

I suggest you consider the DC resistance of a mile (and a mile
back)
of
thin wire.

Telephone wire in the US is usually 24 or 26 gauge. Taking the
worst
case:

26 gauge - 40 ohms/1000 feet = 211 ohms/mile, presuming the return
path
is
a low resistance ground.

The reurn is a length of the same wire.

Yes, the line is usually balanced. So about double the loss to about 5
dB/mile.

Presuming the load is 600 ohms, loss is 0.739 or 2.6 dB.

The load is rarely 600 ohms AIUI.

Do you think it is higher or lower than 600 ohms?


An example is given on page 69 of the book "Transmission Circuits for
Telephonic Communication".

I quote:

"In order to get a clearer idea of what is meant by transformer and
transition losses as well as to get a more concrete idea of their order
of
magnitude, let us consider the case of an e.m.f. E acting through a
sending
end impedance Z1 of 240 - j123 ohms and connected to a receiving end
impedance Z2 of 623 - j350 ohms."

Make of it what you will.

The magnitude of the source is 269 ohms.

The magnitude of the load is 714 ohms

On page 70 and 71, they discuss a test set for comparing transmitters
(carbon microphones, I think). The circuit simulates the sending end
circuitry of a telephone and has 8 miles of cable as well as some
transformers and induction coils (as they called them; they were just
inductors). The impedance driving the telephone line wasn't just the
impedance of the microphone; it was modified by the additional
circuitry.
They then say:

"In this particular circuit the 800 cycle impedance at the transmitter
terminals is approximately 307 - j74 ohms. It is, therefore, seen that
with present commercial types of transmitters, ranging between 30 and
150
ohms in resistance, this circuit will discriminate in favor of the
transmitter having the higher resistance."
-------------------------------------------------------------------------


The magnitude of the source is 315 ohms.


On page 150, they say:

"For example, the 800-cycle iterative impedance of a non-loaded No. 19
gauge cable circuit is approximately 500 @ 45 degrees, and that of a
non-loaded open wire line is about 700 @ 14 degrees ohms."

500 ohms and 700 ohms are impedance magnitudes as is.

Why do you focus on the magnitude of the impedance to the exclusion of
the phase angle? According to the old telephone book I have the phase
angle of the impedance is also important in telephonic transmission.

Just trying to keep it simple. ;-)

[Eeyore]

Arny Krueger wrote:

"Eeyore" wrote
Arny Krueger wrote:
"Eeyore" wrote:
John Byrns wrote:

A Bel or 10 dB seems like an awfully large loss for "a standard
telephone line over the distance of one mile, at 1kHz", is this really
correct?

I suggest you consider the DC resistance of a mile (and a mile back) of
thin wire.

Telephone wire in the US is usually 24 or 26 gauge. Taking the worst
case:

26 gauge - 40 ohms/1000 feet = 211 ohms/mile, presuming the return path
is a low resistance ground.

The reurn is a length of the same wire.

Yes, the line is usually balanced. So about double the loss to about 5
dB/mile.

Presuming the load is 600 ohms, loss is 0.739 or 2.6 dB.

The load is rarely 600 ohms AIUI.

Do you think it is higher or lower than 600 ohms?

I was under the impression it could be lower but I see the standards still refer
to 600 ohms.

The characteristic impedance of the twisted pair cable is actually around 100
ohms and DSL circuits operate at this impedance. So it's 600 ohms for audio and
100 ohms for data.

Graham

[Chris Hornbeck]

On Wed, 22 Aug 2007 03:15:13 +0100, Eeyore
wrote:

Do you think it is higher or lower than 600 ohms?

I was under the impression it could be lower but I see the standards still refer
to 600 ohms.

The characteristic impedance of the twisted pair cable is actually around 100
ohms and DSL circuits operate at this impedance. So it's 600 ohms for audio and
100 ohms for data.

The big numbers are for open-wire line with huge (by modern standards)
spacing. Modern plastic-insulated twisted pairs tend to fall, as
you say, around 100 ohms.

And the World is 72 ohms. The Wires have almost got it right.

Thanks, as always,

Chris Hornbeck
"It's just this little Chromium Switch.
You people are SO superstitious."

[John Byrns]

In article ,
Eeyore wrote:

Arny Krueger wrote:

"Eeyore" wrote
Arny Krueger wrote:
"Eeyore" wrote:
John Byrns wrote:

A Bel or 10 dB seems like an awfully large loss for "a standard
telephone line over the distance of one mile, at 1kHz", is this
really
correct?

I suggest you consider the DC resistance of a mile (and a mile back)
of
thin wire.

Telephone wire in the US is usually 24 or 26 gauge. Taking the worst
case:

26 gauge - 40 ohms/1000 feet = 211 ohms/mile, presuming the return path
is a low resistance ground.

The reurn is a length of the same wire.

Yes, the line is usually balanced. So about double the loss to about 5
dB/mile.

Presuming the load is 600 ohms, loss is 0.739 or 2.6 dB.

The load is rarely 600 ohms AIUI.

Do you think it is higher or lower than 600 ohms?

I was under the impression it could be lower but I see the standards still
refer to 600 ohms.

The characteristic impedance of the twisted pair cable is actually around 100
ohms and DSL circuits operate at this impedance. So it's 600 ohms for audio
and 100 ohms for data.

I believe the problem here is that the characteristic impedance of this
type of cable varies with frequency because it doesn't have enough
inductance. The result is that the characteristic impedance is higher
at voice frequencies than it is at ultrasonic frequencies. Back in the
days when telephone loops were used in radio for remote broadcasts and
linking the studio to the transmitter site, this effect was used to
advantage to equalize short loops by terminating them in 150 Ohms rather
than 600 Ohms. This optimized the transmission at the higher audio
frequencies, where the losses were greater, relative to the lower
frequencies, by mismatching the line at low frequencies while matching
it properly at high frequencies.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[John Byrns]

In article ,
Chris Hornbeck wrote:

On Wed, 22 Aug 2007 03:15:13 +0100, Eeyore
wrote:

Do you think it is higher or lower than 600 ohms?

I was under the impression it could be lower but I see the standards still
refer
to 600 ohms.

The characteristic impedance of the twisted pair cable is actually around
100
ohms and DSL circuits operate at this impedance. So it's 600 ohms for audio
and
100 ohms for data.

The big numbers are for open-wire line with huge (by modern standards)
spacing. Modern plastic-insulated twisted pairs tend to fall, as
you say, around 100 ohms.

While I believe the characteristic impedance of open wire lines is
higher than that of cables, as you say, that is far from the entire
story. The characteristic impedance of cable is greatly dependent on
frequency as a result of not having the correct ratio of inductance to
capacitance. The result is that the characteristic impedance of cable
varies with frequency, being lower at ultrasonic frequencies than at
lower audio frequencies.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[The Phantom]

On Wed, 22 Aug 2007 15:58:52 GMT, John Byrns wrote:

In article ,
Chris Hornbeck wrote:

On Wed, 22 Aug 2007 03:15:13 +0100, Eeyore
wrote:

Do you think it is higher or lower than 600 ohms?

I was under the impression it could be lower but I see the standards still
refer
to 600 ohms.

The characteristic impedance of the twisted pair cable is actually around
100
ohms and DSL circuits operate at this impedance. So it's 600 ohms for audio
and
100 ohms for data.

The big numbers are for open-wire line with huge (by modern standards)
spacing. Modern plastic-insulated twisted pairs tend to fall, as
you say, around 100 ohms.

While I believe the characteristic impedance of open wire lines is
higher than that of cables, as you say, that is far from the entire
story. The characteristic impedance of cable is greatly dependent on
frequency as a result of not having the correct ratio of inductance to
capacitance.

Once you're above the corner frequency, this is no longer true, until the
frequency is very high. See:

http://www.prc68.com/I/Zo.shtml

It's the open wire lines that have the 600 ohm impedance. That is what
they were using in the early days of telephone, and we inherited that 600
ohm legacy for telephone equipment for many years. The example of an open
wire line given on the web page referenced is of a pair of 6 gauge (!!)
wires, 1 foot apart.

The result is that the characteristic impedance of cable
varies with frequency, being lower at ultrasonic frequencies than at
lower audio frequencies.


Regards,

John Byrns

[Eeyore]

John Byrns wrote:

Eeyore wrote:
Arny Krueger wrote:
"Eeyore" wrote
Arny Krueger wrote:
"Eeyore" wrote:
John Byrns wrote:

A Bel or 10 dB seems like an awfully large loss for "a standard
telephone line over the distance of one mile, at 1kHz", is this
really correct?

I suggest you consider the DC resistance of a mile (and a mile back)
of thin wire.

Telephone wire in the US is usually 24 or 26 gauge. Taking the worst
case:

26 gauge - 40 ohms/1000 feet = 211 ohms/mile, presuming the return path
is a low resistance ground.

The reurn is a length of the same wire.

Yes, the line is usually balanced. So about double the loss to about 5
dB/mile.

Presuming the load is 600 ohms, loss is 0.739 or 2.6 dB.

The load is rarely 600 ohms AIUI.

Do you think it is higher or lower than 600 ohms?

I was under the impression it could be lower but I see the standards still
refer to 600 ohms.

The characteristic impedance of the twisted pair cable is actually around 100
ohms and DSL circuits operate at this impedance. So it's 600 ohms for audio
and 100 ohms for data.

I believe the problem here is that the characteristic impedance of this
type of cable varies with frequency because it doesn't have enough
inductance.

The same must be true of Cat5 etc in that case. In nay case, the charcteristic
impedance is AIUI simply determined by the physical properties of the line
(conductor dia and spacing notably).


Graham

[John Byrns]

In article ,
The Phantom wrote:

On Wed, 22 Aug 2007 15:58:52 GMT, John Byrns wrote:

In article ,
Chris Hornbeck wrote:

On Wed, 22 Aug 2007 03:15:13 +0100, Eeyore
wrote:

Do you think it is higher or lower than 600 ohms?

I was under the impression it could be lower but I see the standards
still
refer
to 600 ohms.

The characteristic impedance of the twisted pair cable is actually around
100
ohms and DSL circuits operate at this impedance. So it's 600 ohms for
audio
and
100 ohms for data.

The big numbers are for open-wire line with huge (by modern standards)
spacing. Modern plastic-insulated twisted pairs tend to fall, as
you say, around 100 ohms.

While I believe the characteristic impedance of open wire lines is
higher than that of cables, as you say, that is far from the entire
story. The characteristic impedance of cable is greatly dependent on
frequency as a result of not having the correct ratio of inductance to
capacitance.

Once you're above the corner frequency, this is no longer true, until the
frequency is very high. See:

http://www.prc68.com/I/Zo.shtml

Please note the second paragraph in the above referenced web page which
states, "It turns out the the "100 Ohm" UTP cable does have a
characteristic impedance near 600 Ohms at 1 kHz."

Note also that the "corner frequency" for UTP is about 51 kHz, while
this discussion concerns the characteristic impedance at audio
frequencies which are well below 51 kHz. This is the reason I used the
word "ultrasonic", rather than "RF", to refer to frequencies above the
audio band. As a point of interest, the "standard" cable that started
this discussion has a "corner frequency" of about 13.7 kHz if I pushed
the buttons on my calculator correctly.

It's the open wire lines that have the 600 ohm impedance. That is what
they were using in the early days of telephone, and we inherited that 600
ohm legacy for telephone equipment for many years. The example of an open
wire line given on the web page referenced is of a pair of 6 gauge (!!)
wires, 1 foot apart.

The result is that the characteristic impedance of cable
varies with frequency, being lower at ultrasonic frequencies than at
lower audio frequencies.

If the above referenced web page is to be believed, then it appears that
600 Ohms is also a good approximation for the characteristic impedance
of "100 Ohm UTP" in the audio band.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Eeyore]

John Byrns wrote:

Please note the second paragraph in the above referenced web page which
states, "It turns out the the "100 Ohm" UTP cable does have a
characteristic impedance near 600 Ohms at 1 kHz."

And the relevance of this to say a 1 km or 5 km run of cable is ?

How many times do you have to be told ? Short runs are not 'transmission lines'.

Graham

[Eeyore]

John Byrns wrote:

If the above referenced web page is to be believed, then it appears that
600 Ohms is also a good approximation for the characteristic impedance
of "100 Ohm UTP" in the audio band.

At what cable length ?

Graham

[Chris Hornbeck]

On Thu, 23 Aug 2007 03:25:34 +0100, Eeyore
wrote:

Short runs are not 'transmission lines'.

And characteristic impedances are defined (circularly,
but that's the deal) as infinitely long (or terminated
in the characteristic impedance).

There is no such critter as a length variable in
characteristic impedance. It's a function of
geometry and a coupla materials variables.


Such a messy thread that Angels fear to tread, but
transmission line losses are only resistive at DC, and
are complicated (frequency-sensitive) into matched loading.
Into unmatched loading, they're beyond Usenet generalzation.


Thanks, as always,

Chris Hornbeck
"It's just this little Chromium Switch.
You people are SO superstitious."

[John Byrns]

In article ,
Eeyore wrote:

John Byrns wrote:

Please note the second paragraph in the above referenced web page which
states, "It turns out the the "100 Ohm" UTP cable does have a
characteristic impedance near 600 Ohms at 1 kHz."

And the relevance of this to say a 1 km or 5 km run of cable is ?

My example was a 5 mile local loop, not 5 km. Are you still trying to
tell me that a 5 mile, or even 5 km, local loop, or run of "UTP" cable,
is no different than a simple resistor whose resistance is equal to the
DC loop resistance of the cable?

How many times do you have to be told ? Short runs are not 'transmission
lines'.

You still haven't told us what a "transmission line" is, and how long a
cable must be for you to consider it to be a "transmission line"?


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[John Byrns]

In article ,
Eeyore wrote:

John Byrns wrote:

If the above referenced web page is to be believed, then it appears that
600 Ohms is also a good approximation for the characteristic impedance
of "100 Ohm UTP" in the audio band.

At what cable length ?

Any length. The characteristic impedance is independent of length
because it is defined in terms of the cables R, L, C, & G per unit
length, where the unit length is your choice.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Eeyore]

John Byrns wrote:

Eeyore wrote:
John Byrns wrote:

Please note the second paragraph in the above referenced web page which
states, "It turns out the the "100 Ohm" UTP cable does have a
characteristic impedance near 600 Ohms at 1 kHz."

And the relevance of this to say a 1 km or 5 km run of cable is ?

My example was a 5 mile local loop, not 5 km.

Do you normally pick nits ? 5 mi = 8km more or less.

The 'mile' is only used in 2 developed countries worlwide (and only for motoring
in one of them) out of hundreds who use metric measure. Do you have an aversion
to using international standard (SI) units ?


Are you still trying to tell me that a 5 mile, or even 5 km, local loop, or
run of "UTP" cable,
is no different than a simple resistor whose resistance is equal to the
DC loop resistance of the cable?

No, I never ever said that. What I implied (correctly) was that for shorter
lengths, the DC resisitive losses in real telephone cables at audio frequencies
dominate the attenuation figures. I simply never mentioned the other aspects (to
avoid unnecessary and pointless complexity).


How many times do you have to be told ? Short runs are not 'transmission
lines'.

You still haven't told us what a "transmission line" is, and how long a
cable must be for you to consider it to be a "transmission line"?

How long is a piece of string ? In order for a cable to even begin to behave as
a transmission line, its length must be some modest fraction of the highest
frequency's wavelength. For telephones. the highest frequency of interest is
4kHz and its wavelength is 75km.

I suggest you also wake up to the idea that twisted pair cables are not some
fanciful '600 ohm' circuit.

Graham

[Eeyore]

John Byrns wrote:

Eeyore wrote:
John Byrns wrote:

If the above referenced web page is to be believed, then it appears that
600 Ohms is also a good approximation for the characteristic impedance
of "100 Ohm UTP" in the audio band.

At what cable length ?

Any length.

1 metre ?

You're an utter ****WIT !

I suggest you depart this group with your head held in shame for being a total
cretin.

Graham

[The Phantom]

On Wed, 22 Aug 2007 17:16:51 -0500, John Byrns
wrote:

In article ,
The Phantom wrote:

On Wed, 22 Aug 2007 15:58:52 GMT, John Byrns wrote:

In article ,
Chris Hornbeck wrote:

On Wed, 22 Aug 2007 03:15:13 +0100, Eeyore
wrote:

Do you think it is higher or lower than 600 ohms?

I was under the impression it could be lower but I see the standards
still
refer
to 600 ohms.

The characteristic impedance of the twisted pair cable is actually around
100
ohms and DSL circuits operate at this impedance. So it's 600 ohms for
audio
and
100 ohms for data.

The big numbers are for open-wire line with huge (by modern standards)
spacing. Modern plastic-insulated twisted pairs tend to fall, as
you say, around 100 ohms.

While I believe the characteristic impedance of open wire lines is
higher than that of cables, as you say, that is far from the entire
story. The characteristic impedance of cable is greatly dependent on
frequency as a result of not having the correct ratio of inductance to
capacitance.

Once you're above the corner frequency, this is no longer true, until the
frequency is very high. See:

http://www.prc68.com/I/Zo.shtml

Please note the second paragraph in the above referenced web page which
states, "It turns out the the "100 Ohm" UTP cable does have a
characteristic impedance near 600 Ohms at 1 kHz."

Note also that the "corner frequency" for UTP is about 51 kHz, while
this discussion concerns the characteristic impedance at audio
frequencies

You made an unqualified statement that "The characteristic impedance of
cable is greatly dependent on frequency as a result of not having the
correct ratio of inductance to capacitance." It is true that the
discussion had concerned voice band frequencies, but I felt that it should
be emphasized that your unqualified statement wasn't really true for all
frequencies.

All of my posts until now have concerned early telephone transmission
lines, and I have been at pains to point out that the 600 ohms was a
characteristic of open wire lines. The corner frequency of the open wire
line mentioned on the cited web page is 194 Hz, so the 600 ohm impedance is
fairly constant across the standard telephone voice band. But this is not
the case for CAT5 cable, for example.

Nobody had yet pointed out that transmission line impedance behaves very
differently below the corner frequency than above it.

For example, if you use the values for R, L, G, and C for CAT5 from the web
page cited, and calculate the Zo for a number of frequencies, you get
(using for "angle"):

Frequency Zo

20 Hz 5508.1 -44.989 degrees
100 Hz 2463.3 -44.944
1000 Hz 779.0 -44.439
10000 Hz 249.7 -39.460
20000 Hz 180.5 -34.306
51000 Hz 129.7 -22.518
100000 Hz 115.5 -13.525
1000000 Hz 109.1 -1.462
10000000 Hz 109.0 -0.146
100000000 Hz 109.0 -0.015

Eeyore said in another post that "The characteristic impedance of the
twisted pair cable is actually around 100 ohms and DSL circuits operate at
this impedance. So it's 600 ohms for audio and 100 ohms for data."

SNIP

And, you said:

If the above referenced web page is to be believed, then it appears that
600 Ohms is also a good approximation for the characteristic impedance
of "100 Ohm UTP" in the audio band.

Apparently not, with 5508 ohms at 20 Hz and 180.5 ohms at 20000 Hz.

Even in the telephone voice band with an impedance of 1422 ohms at 300 Hz
and 450 ohms at 3000 Hz, I wouldn't call 600 ohms a "good" approximation.

These numbers are for CAT5; UTP may be a little different, but it will
still have a substantial variation in impedance over the audio band. In
fact, you yourself said, "The characteristic impedance of cable is greatly
dependent on frequency...", referring to frequencies below the corner
frequency of the cable. If this is so, then no single impedance is going
to be a good approximation of the cable impedance in the audio band.

The fact that UTP has an impedance of "...near 600 ohms at 1 kHz." (as
the web page says) has no connection to the fact that the early 20th
century open wire lines had an impedance of ~600 ohms. The early lines
were being operated above their corner frequency, where they behaved like
"proper" transmission lines, with a Zo over the telephone band that was
much more constant than twisted pair. Calculating the Zo of the open wire
line whose parameters are given on the cited web page:

Frequency Zo

300 Hz 662.3 -16.45 degrees
800 Hz 615.6 -6.82
1500 Hz 609.4 -3.69
3000 Hz 607.5 -1.85

All this got going because Iain mistakenly equated the loss of 1 mile of
phone line with 1 bel. We now know he was off by a factor of 10.



Regards,

John Byrns

[Arny Krueger]

"John Byrns" wrote in message
...
In article ,
Eeyore wrote:

John Byrns wrote:

Please note the second paragraph in the above referenced web page which
states, "It turns out the the "100 Ohm" UTP cable does have a
characteristic impedance near 600 Ohms at 1 kHz."

And the relevance of this to say a 1 km or 5 km run of cable is ?

My example was a 5 mile local loop, not 5 km. Are you still trying to
tell me that a 5 mile, or even 5 km, local loop, or run of "UTP" cable,
is no different than a simple resistor whose resistance is equal to the
DC loop resistance of the cable?

No, but how significant length is depends on the signal frequency.

How many times do you have to be told ? Short runs are not 'transmission
lines'.

You still haven't told us what a "transmission line" is, and how long a
cable must be for you to consider it to be a "transmission line"?

The really picky folks on the Usenet audio jury say that to be a
transmission line, the line has to be 1/8 or more of a wavelength long at
the highest frequency transmitted.

For a voice-grade signal topping out at say 4 KHz, a wavelength is about 46
miles, so anything up to about 6 miles is most definitely not a transmission
line. For high fidelity audio, drop that to abut 2 miles.

[Phil Allison]

"Arny Krueger"

The really picky folks on the Usenet audio jury say that to be a
transmission line, the line has to be 1/8 or more of a wavelength long at
the highest frequency transmitted.

For a voice-grade signal topping out at say 4 KHz, a wavelength is about
46 miles, so anything up to about 6 miles is most definitely not a
transmission line. For high fidelity audio, drop that to abut 2 miles.


** Then, there are the relatively SANE folk who see * that extreme
position * as being extraordinarily pedantic, artificial and entirely
foolish.

The most perspicacious of that latter group assert that this position is
blatant heresy, promulgated by a subset of the RF fraternity -
particularly the great unwashed, smelly and un-educated " ham radio "
rabble.

Well, **** them - hams are just pigs with a bad attitude.

Co-axial, twisted pair and even twin-line cables all exhibit "
characteristic impedance" phenomena at lengths that are FAR , FAR shorter
than that needed for standing wave effects.

Distributed capacitance, inductance and resistive losses are very
significant at high audio frequencies, even with cables of only a few
metres, if the load impedance is that of a ES loudspeaker.

500 metres of unloaded, shielded twisted pair mic cable exhibits all the
debilitating effects of a badly terminated transmission line - despite the
shortest wavelength being a TINY fraction its length.

Either DO some simple bench tests, or do the maths on a good simulator.

Correctly terminating audio cables does wonders for their flat response
bandwidth.

Failing to do so can bite, sometimes very hard.






........ Phil

[The Phantom]

On Thu, 23 Aug 2007 08:10:04 -0400, "Arny Krueger"
wrote:


"John Byrns" wrote in message
...
In article ,
Eeyore wrote:

John Byrns wrote:

Please note the second paragraph in the above referenced web page which
states, "It turns out the the "100 Ohm" UTP cable does have a
characteristic impedance near 600 Ohms at 1 kHz."

And the relevance of this to say a 1 km or 5 km run of cable is ?

My example was a 5 mile local loop, not 5 km. Are you still trying to
tell me that a 5 mile, or even 5 km, local loop, or run of "UTP" cable,
is no different than a simple resistor whose resistance is equal to the
DC loop resistance of the cable?

No, but how significant length is depends on the signal frequency.

How many times do you have to be told ? Short runs are not 'transmission
lines'.

You still haven't told us what a "transmission line" is, and how long a
cable must be for you to consider it to be a "transmission line"?

The really picky folks on the Usenet audio jury say that to be a
transmission line, the line has to be 1/8 or more of a wavelength long at
the highest frequency transmitted.

For a voice-grade signal topping out at say 4 KHz, a wavelength is about 46
miles, so anything up to about 6 miles is most definitely not a transmission
line. For high fidelity audio, drop that to abut 2 miles.

This would be about right for that open wire line consisting of a pair of 6
gauge conductors spaced 1 foot apart.

For a twisted pair of 19 gauge or 22 gauge, the velocity of propagation is
significantly lower, and your numbers would be much smaller.

[John Byrns]

In article ,
The Phantom wrote:

On Wed, 22 Aug 2007 17:16:51 -0500, John Byrns
wrote:

In article ,
The Phantom wrote:

On Wed, 22 Aug 2007 15:58:52 GMT, John Byrns wrote:

In article ,
Chris Hornbeck wrote:

On Wed, 22 Aug 2007 03:15:13 +0100, Eeyore
wrote:

Do you think it is higher or lower than 600 ohms?

I was under the impression it could be lower but I see the standards
still
refer
to 600 ohms.

The characteristic impedance of the twisted pair cable is actually
around
100
ohms and DSL circuits operate at this impedance. So it's 600 ohms for
audio
and
100 ohms for data.

The big numbers are for open-wire line with huge (by modern standards)
spacing. Modern plastic-insulated twisted pairs tend to fall, as
you say, around 100 ohms.

While I believe the characteristic impedance of open wire lines is
higher than that of cables, as you say, that is far from the entire
story. The characteristic impedance of cable is greatly dependent on
frequency as a result of not having the correct ratio of inductance to
capacitance.

Once you're above the corner frequency, this is no longer true, until
the
frequency is very high. See:

http://www.prc68.com/I/Zo.shtml

Please note the second paragraph in the above referenced web page which
states, "It turns out the the "100 Ohm" UTP cable does have a
characteristic impedance near 600 Ohms at 1 kHz."

Note also that the "corner frequency" for UTP is about 51 kHz, while
this discussion concerns the characteristic impedance at audio
frequencies

You made an unqualified statement that "The characteristic impedance of
cable is greatly dependent on frequency as a result of not having the
correct ratio of inductance to capacitance." It is true that the
discussion had concerned voice band frequencies, but I felt that it should
be emphasized that your unqualified statement wasn't really true for all
frequencies.

All of my posts until now have concerned early telephone transmission
lines, and I have been at pains to point out that the 600 ohms was a
characteristic of open wire lines. The corner frequency of the open wire
line mentioned on the cited web page is 194 Hz, so the 600 ohm impedance is
fairly constant across the standard telephone voice band. But this is not
the case for CAT5 cable, for example.

Nobody had yet pointed out that transmission line impedance behaves very
differently below the corner frequency than above it.

For example, if you use the values for R, L, G, and C for CAT5 from the web
page cited, and calculate the Zo for a number of frequencies, you get
(using for "angle"):

Frequency Zo

20 Hz 5508.1 -44.989 degrees
100 Hz 2463.3 -44.944
1000 Hz 779.0 -44.439
10000 Hz 249.7 -39.460
20000 Hz 180.5 -34.306
51000 Hz 129.7 -22.518
100000 Hz 115.5 -13.525
1000000 Hz 109.1 -1.462
10000000 Hz 109.0 -0.146
100000000 Hz 109.0 -0.015

Eeyore said in another post that "The characteristic impedance of the
twisted pair cable is actually around 100 ohms and DSL circuits operate at
this impedance. So it's 600 ohms for audio and 100 ohms for data."

SNIP

And, you said:

If the above referenced web page is to be believed, then it appears that
600 Ohms is also a good approximation for the characteristic impedance
of "100 Ohm UTP" in the audio band.

Apparently not, with 5508 ohms at 20 Hz and 180.5 ohms at 20000 Hz.

Even in the telephone voice band with an impedance of 1422 ohms at 300 Hz
and 450 ohms at 3000 Hz, I wouldn't call 600 ohms a "good" approximation.

These numbers are for CAT5; UTP may be a little different, but it will
still have a substantial variation in impedance over the audio band. In
fact, you yourself said, "The characteristic impedance of cable is greatly
dependent on frequency...", referring to frequencies below the corner
frequency of the cable. If this is so, then no single impedance is going
to be a good approximation of the cable impedance in the audio band.

The fact that UTP has an impedance of "...near 600 ohms at 1 kHz." (as
the web page says) has no connection to the fact that the early 20th
century open wire lines had an impedance of ~600 ohms. The early lines
were being operated above their corner frequency, where they behaved like
"proper" transmission lines, with a Zo over the telephone band that was
much more constant than twisted pair. Calculating the Zo of the open wire
line whose parameters are given on the cited web page:

Frequency Zo

300 Hz 662.3 -16.45 degrees
800 Hz 615.6 -6.82
1500 Hz 609.4 -3.69
3000 Hz 607.5 -1.85

All this got going because Iain mistakenly equated the loss of 1 mile of
phone line with 1 bel. We now know he was off by a factor of 10.

Since several posters have mentioned open wire line, it is worth
mentioning that the "standard telephone line" Iain was referring to was
probably 19 gauge cable, not open wire line, as open wire line has a
loss much lower than 1 decibel per mile.

Relative to the considerable variation in the characteristic impedance
of telephone cables vs. frequency, I pointed this out and indicated how
advantage could be taken of the variation in the characteristic
impedance vs. frequency to help equalize short loops by terminating the
line in its characteristic impedance at the high end of the band, rather
than terminating it with the "600 Ohm" midband impedance.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[John Byrns]

In article ,
"Arny Krueger" wrote:

"John Byrns" wrote in message
...
In article ,
Eeyore wrote:

John Byrns wrote:

Please note the second paragraph in the above referenced web page which
states, "It turns out the the "100 Ohm" UTP cable does have a
characteristic impedance near 600 Ohms at 1 kHz."

And the relevance of this to say a 1 km or 5 km run of cable is ?

My example was a 5 mile local loop, not 5 km. Are you still trying to
tell me that a 5 mile, or even 5 km, local loop, or run of "UTP" cable,
is no different than a simple resistor whose resistance is equal to the
DC loop resistance of the cable?

No, but how significant length is depends on the signal frequency.

How many times do you have to be told ? Short runs are not 'transmission
lines'.

You still haven't told us what a "transmission line" is, and how long a
cable must be for you to consider it to be a "transmission line"?

The really picky folks on the Usenet audio jury say that to be a
transmission line, the line has to be 1/8 or more of a wavelength long at
the highest frequency transmitted.

Thanks Arny, finally someone offers a number for how long a line must be
to be considered a "transmission line", I wonder what Eyeore thinks of
this number?

For a voice-grade signal topping out at say 4 KHz, a wavelength is about 46
miles, so anything up to about 6 miles is most definitely not a transmission
line. For high fidelity audio, drop that to abut 2 miles.

You are forgetting that the propagation velocity of a wave in the
"standard telephone line" cable, that Iain mentioned in the original
version of his "decibel" web page, is about one quarter the speed of
light in free space. That makes a wavelength at 4 kHz somewhere in the
eleven to twelve mile range, using your 1/8 wavelength factor that would
make any length of this cable over about 1.5 miles long a "transmission
line", and shorter for Hi-Fi audio.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Arny Krueger]

"John Byrns" wrote in message

In article ,
"Arny Krueger" wrote:

"John Byrns" wrote in message
...
In article ,
Eeyore wrote:

John Byrns wrote:

Please note the second paragraph in the above
referenced web page which states, "It turns out the
the "100 Ohm" UTP cable does have a characteristic
impedance near 600 Ohms at 1 kHz."

And the relevance of this to say a 1 km or 5 km run of
cable is ?

My example was a 5 mile local loop, not 5 km. Are you
still trying to tell me that a 5 mile, or even 5 km,
local loop, or run of "UTP" cable, is no different than
a simple resistor whose resistance is equal to the DC
loop resistance of the cable?

No, but how significant length is depends on the signal
frequency.

How many times do you have to be told ? Short runs are
not 'transmission lines'.

You still haven't told us what a "transmission line"
is, and how long a cable must be for you to consider it
to be a "transmission line"?

The really picky folks on the Usenet audio jury say that
to be a transmission line, the line has to be 1/8 or
more of a wavelength long at the highest frequency
transmitted.

Thanks Arny, finally someone offers a number for how long
a line must be to be considered a "transmission line", I
wonder what Eyeore thinks of this number?

For a voice-grade signal topping out at say 4 KHz, a
wavelength is about 46 miles, so anything up to about 6
miles is most definitely not a transmission line. For
high fidelity audio, drop that to abut 2 miles.

You are forgetting that the propagation velocity of a
wave in the "standard telephone line" cable, that Iain
mentioned in the original version of his "decibel" web
page, is about one quarter the speed of light in free
space.

Yeah, I forgot propigation delay, but my sources say that the propigation
coefficient of UTP 24 gauge is more like 70% than 25%.

[John Byrns]

In article ,
"Arny Krueger" wrote:

"John Byrns" wrote in message

In article ,
"Arny Krueger" wrote:

"John Byrns" wrote in message
...
In article ,
Eeyore wrote:

John Byrns wrote:

Please note the second paragraph in the above
referenced web page which states, "It turns out the
the "100 Ohm" UTP cable does have a characteristic
impedance near 600 Ohms at 1 kHz."

And the relevance of this to say a 1 km or 5 km run of
cable is ?

My example was a 5 mile local loop, not 5 km. Are you
still trying to tell me that a 5 mile, or even 5 km,
local loop, or run of "UTP" cable, is no different than
a simple resistor whose resistance is equal to the DC
loop resistance of the cable?

No, but how significant length is depends on the signal
frequency.

How many times do you have to be told ? Short runs are
not 'transmission lines'.

You still haven't told us what a "transmission line"
is, and how long a cable must be for you to consider it
to be a "transmission line"?

The really picky folks on the Usenet audio jury say that
to be a transmission line, the line has to be 1/8 or
more of a wavelength long at the highest frequency
transmitted.

Thanks Arny, finally someone offers a number for how long
a line must be to be considered a "transmission line", I
wonder what Eyeore thinks of this number?

For a voice-grade signal topping out at say 4 KHz, a
wavelength is about 46 miles, so anything up to about 6
miles is most definitely not a transmission line. For
high fidelity audio, drop that to abut 2 miles.

You are forgetting that the propagation velocity of a
wave in the "standard telephone line" cable, that Iain
mentioned in the original version of his "decibel" web
page, is about one quarter the speed of light in free
space.

Yeah, I forgot propigation delay, but my sources say that the propigation
coefficient of UTP 24 gauge is more like 70% than 25%.

That may well be correct, the approx. 25% figure I gave is for the
"standard telephone line" that Iain referred to on the first version of
his web page. I am surprised though that the wave velocity is so
different in the old 19 gauge cable vs. 24 gauge UTP.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[The Phantom]

On Thu, 23 Aug 2007 15:11:49 -0400, "Arny Krueger"
wrote:

"John Byrns" wrote in message

In article ,
"Arny Krueger" wrote:

"John Byrns" wrote in message
...
In article ,
Eeyore wrote:

John Byrns wrote:

Please note the second paragraph in the above
referenced web page which states, "It turns out the
the "100 Ohm" UTP cable does have a characteristic
impedance near 600 Ohms at 1 kHz."

And the relevance of this to say a 1 km or 5 km run of
cable is ?

My example was a 5 mile local loop, not 5 km. Are you
still trying to tell me that a 5 mile, or even 5 km,
local loop, or run of "UTP" cable, is no different than
a simple resistor whose resistance is equal to the DC
loop resistance of the cable?

No, but how significant length is depends on the signal
frequency.

How many times do you have to be told ? Short runs are
not 'transmission lines'.

You still haven't told us what a "transmission line"
is, and how long a cable must be for you to consider it
to be a "transmission line"?

The really picky folks on the Usenet audio jury say that
to be a transmission line, the line has to be 1/8 or
more of a wavelength long at the highest frequency
transmitted.

Thanks Arny, finally someone offers a number for how long
a line must be to be considered a "transmission line", I
wonder what Eyeore thinks of this number?

For a voice-grade signal topping out at say 4 KHz, a
wavelength is about 46 miles, so anything up to about 6
miles is most definitely not a transmission line. For
high fidelity audio, drop that to abut 2 miles.

You are forgetting that the propagation velocity of a
wave in the "standard telephone line" cable, that Iain
mentioned in the original version of his "decibel" web
page, is about one quarter the speed of light in free
space.

Yeah, I forgot propigation delay, but my sources say that the propigation
coefficient of UTP 24 gauge is more like 70% than 25%.

This is only true at high frequencies. The classic condition for
"distortionless" transmission is for the line parameters R, L, G and C to
be related as:

L C
- = -
R G

Since most real cables have G essentially zero at low frequencies, this
causes the propagation delay to vary with frequency in the audio band.

However, modern cables are probably better in this respect than the 1925
cables whose properties I copied out of the old book I've been referencing,
but their Zo and propagation delay still vary with frequency. Both of
these effects are due to the above relationship not being met.

[The Phantom]

On Thu, 23 Aug 2007 14:14:53 GMT, John Byrns wrote:

In article ,
The Phantom wrote:

On Wed, 22 Aug 2007 17:16:51 -0500, John Byrns
wrote:

In article ,
The Phantom wrote:

On Wed, 22 Aug 2007 15:58:52 GMT, John Byrns wrote:

In article ,
Chris Hornbeck wrote:

On Wed, 22 Aug 2007 03:15:13 +0100, Eeyore
wrote:

Do you think it is higher or lower than 600 ohms?

I was under the impression it could be lower but I see the standards
still
refer
to 600 ohms.

The characteristic impedance of the twisted pair cable is actually
around
100
ohms and DSL circuits operate at this impedance. So it's 600 ohms for
audio
and
100 ohms for data.

The big numbers are for open-wire line with huge (by modern standards)
spacing. Modern plastic-insulated twisted pairs tend to fall, as
you say, around 100 ohms.

While I believe the characteristic impedance of open wire lines is
higher than that of cables, as you say, that is far from the entire
story. The characteristic impedance of cable is greatly dependent on
frequency as a result of not having the correct ratio of inductance to
capacitance.

Once you're above the corner frequency, this is no longer true, until
the
frequency is very high. See:

http://www.prc68.com/I/Zo.shtml

Please note the second paragraph in the above referenced web page which
states, "It turns out the the "100 Ohm" UTP cable does have a
characteristic impedance near 600 Ohms at 1 kHz."

Note also that the "corner frequency" for UTP is about 51 kHz, while
this discussion concerns the characteristic impedance at audio
frequencies

You made an unqualified statement that "The characteristic impedance of
cable is greatly dependent on frequency as a result of not having the
correct ratio of inductance to capacitance." It is true that the
discussion had concerned voice band frequencies, but I felt that it should
be emphasized that your unqualified statement wasn't really true for all
frequencies.

All of my posts until now have concerned early telephone transmission
lines, and I have been at pains to point out that the 600 ohms was a
characteristic of open wire lines. The corner frequency of the open wire
line mentioned on the cited web page is 194 Hz, so the 600 ohm impedance is
fairly constant across the standard telephone voice band. But this is not
the case for CAT5 cable, for example.

Nobody had yet pointed out that transmission line impedance behaves very
differently below the corner frequency than above it.

For example, if you use the values for R, L, G, and C for CAT5 from the web
page cited, and calculate the Zo for a number of frequencies, you get
(using for "angle"):

Frequency Zo

20 Hz 5508.1 -44.989 degrees
100 Hz 2463.3 -44.944
1000 Hz 779.0 -44.439
10000 Hz 249.7 -39.460
20000 Hz 180.5 -34.306
51000 Hz 129.7 -22.518
100000 Hz 115.5 -13.525
1000000 Hz 109.1 -1.462
10000000 Hz 109.0 -0.146
100000000 Hz 109.0 -0.015

Eeyore said in another post that "The characteristic impedance of the
twisted pair cable is actually around 100 ohms and DSL circuits operate at
this impedance. So it's 600 ohms for audio and 100 ohms for data."

SNIP

And, you said:

If the above referenced web page is to be believed, then it appears that
600 Ohms is also a good approximation for the characteristic impedance
of "100 Ohm UTP" in the audio band.

Apparently not, with 5508 ohms at 20 Hz and 180.5 ohms at 20000 Hz.

Even in the telephone voice band with an impedance of 1422 ohms at 300 Hz
and 450 ohms at 3000 Hz, I wouldn't call 600 ohms a "good" approximation.

These numbers are for CAT5; UTP may be a little different, but it will
still have a substantial variation in impedance over the audio band. In
fact, you yourself said, "The characteristic impedance of cable is greatly
dependent on frequency...", referring to frequencies below the corner
frequency of the cable. If this is so, then no single impedance is going
to be a good approximation of the cable impedance in the audio band.

The fact that UTP has an impedance of "...near 600 ohms at 1 kHz." (as
the web page says) has no connection to the fact that the early 20th
century open wire lines had an impedance of ~600 ohms. The early lines
were being operated above their corner frequency, where they behaved like
"proper" transmission lines, with a Zo over the telephone band that was
much more constant than twisted pair. Calculating the Zo of the open wire
line whose parameters are given on the cited web page:

Frequency Zo

300 Hz 662.3 -16.45 degrees
800 Hz 615.6 -6.82
1500 Hz 609.4 -3.69
3000 Hz 607.5 -1.85

All this got going because Iain mistakenly equated the loss of 1 mile of
phone line with 1 bel. We now know he was off by a factor of 10.

Since several posters have mentioned open wire line, it is worth
mentioning that the "standard telephone line" Iain was referring to was
probably 19 gauge cable, not open wire line, as open wire line has a
loss much lower than 1 decibel per mile.

I'm sure that was what was meant by "standard telephone line". That was
what was described in the paragraph I copied out of the old Bell Labs book
in my first post in this thread:

"Standard cable is defined as a cable having uniformly distributed
resistances of 88 ohms per loop mile and uniformly distributed shunt
capacitance of .054 microfarad per mile. Its series inductance and shunt
leakance are assumed to be zero."

The 88 ohms per loop mile corresponds to 19 gauge wire. This is the
cable that has .947 dB loss per mile as shown in the table I copied out of
the book.

And it's true that open wire line has much less loss. Terman's "Radio
Engineers' Handbook" has a chart showing the loss of two wire open line. A
line composed of 12 gauge wire with separation to give 600 ohms has an
attenuation of .01 dB per 1000 feet. You can see why before repeaters were
practical they were using 6 gauge wire for long distance lines.

The book describes the earliest repeater amplifiers as consisting of a
telephone receiver (earpiece) with a microphone (carbon button)
mechanically connected to the diaphragm. They say, "The tendency of
microphone buttons to "breathe", due to heating and packing, and the
distortion inherent in carbon buttons make even the best-designed of such
devices difficult to maintain when several are operated in one system."

I can just imagine!


Relative to the considerable variation in the characteristic impedance
of telephone cables vs. frequency, I pointed this out and indicated how
advantage could be taken of the variation in the characteristic
impedance vs. frequency to help equalize short loops by terminating the
line in its characteristic impedance at the high end of the band, rather
than terminating it with the "600 Ohm" midband impedance.

What I was getting at is that with the substantial variation in Zo in the
audio band, your statement "it appears that 600 Ohms is also a good
approximation for the characteristic impedance of "100 Ohm UTP" in the
audio band." rather stretches the meaning of "good approximation".



Regards,

John Byrns

[The Phantom]

On Thu, 23 Aug 2007 15:36:26 -0500, John Byrns
wrote:

In article ,
"Arny Krueger" wrote:

"John Byrns" wrote in message

In article ,
"Arny Krueger" wrote:

"John Byrns" wrote in message
...
In article ,
Eeyore wrote:

John Byrns wrote:

Please note the second paragraph in the above
referenced web page which states, "It turns out the
the "100 Ohm" UTP cable does have a characteristic
impedance near 600 Ohms at 1 kHz."

And the relevance of this to say a 1 km or 5 km run of
cable is ?

My example was a 5 mile local loop, not 5 km. Are you
still trying to tell me that a 5 mile, or even 5 km,
local loop, or run of "UTP" cable, is no different than
a simple resistor whose resistance is equal to the DC
loop resistance of the cable?

No, but how significant length is depends on the signal
frequency.

How many times do you have to be told ? Short runs are
not 'transmission lines'.

You still haven't told us what a "transmission line"
is, and how long a cable must be for you to consider it
to be a "transmission line"?

The really picky folks on the Usenet audio jury say that
to be a transmission line, the line has to be 1/8 or
more of a wavelength long at the highest frequency
transmitted.

Thanks Arny, finally someone offers a number for how long
a line must be to be considered a "transmission line", I
wonder what Eyeore thinks of this number?

For a voice-grade signal topping out at say 4 KHz, a
wavelength is about 46 miles, so anything up to about 6
miles is most definitely not a transmission line. For
high fidelity audio, drop that to abut 2 miles.

You are forgetting that the propagation velocity of a
wave in the "standard telephone line" cable, that Iain
mentioned in the original version of his "decibel" web
page, is about one quarter the speed of light in free
space.

Yeah, I forgot propigation delay, but my sources say that the propigation
coefficient of UTP 24 gauge is more like 70% than 25%.

That may well be correct, the approx. 25% figure I gave is for the
"standard telephone line" that Iain referred to on the first version of
his web page. I am surprised though that the wave velocity is so
different in the old 19 gauge cable vs. 24 gauge UTP.

I suspect the velocity Arny cited isn't for the audio band, whereas the
figure for the old 19 gauge cable was for the telephone voice band.



Regards,

John Byrns

[Eeyore]

Phil Allison wrote:

Distributed capacitance, inductance and resistive losses are very
significant at high audio frequencies, even with cables of only a few
metres, if the load impedance is that of a ES loudspeaker.

Yet modelling them as 'transmission lines' will make us none the wiser.

The specific losses need to be considered according to application.

Graham

[Eeyore]

John Byrns wrote:

"Arny Krueger" wrote:

Yeah, I forgot propigation delay, but my sources say that the propigation
coefficient of UTP 24 gauge is more like 70% than 25%.

That may well be correct, the approx. 25% figure I gave is for the
"standard telephone line" that Iain referred to on the first version of
his web page.

Actually, that's a *telegraph* line. It has no meaningful relationship whatever
to modern audio circuits of any type. I suggest you forget it. This is the
trouble with using 1920's thinking.

Graham

[Phil Allison]

"Eeysore ****ing SNIPPING Idiot "


Phil Allison wrote:


** A lot more than this one para:


Distributed capacitance, inductance and resistive losses are very
significant at high audio frequencies, even with cables of only a few
metres, if the load impedance is that of a ES loudspeaker.

Yet modelling them as 'transmission lines' will make us none the wiser.

** False assertion.

Another one from the donkey brain TROLL.


**Here is what I wrote;

Co-axial, twisted pair and even twin-line cables all exhibit "
characteristic impedance" phenomena at lengths that are FAR , FAR shorter
than that needed for standing wave effects.

Distributed capacitance, inductance and resistive losses are very
significant at high audio frequencies, even with cables of only a few
metres, if the load impedance is that of a ES loudspeaker.

500 metres of unloaded, shielded twisted pair mic cable exhibits all the
debilitating effects of a badly terminated transmission line - despite the
shortest wavelength being a TINY fraction its length.

Either DO some simple bench tests, or do the maths on a good simulator.

Correctly terminating audio cables does wonders for their flat response
bandwidth.

Failing to do so can bite, sometimes very hard.



........ Phil

[John Byrns]

In article ,
Eeyore wrote:

Phil Allison wrote:

Distributed capacitance, inductance and resistive losses are very
significant at high audio frequencies, even with cables of only a few
metres, if the load impedance is that of a ES loudspeaker.

Yet modelling them as 'transmission lines' will make us none the wiser.

How do you suggest modeling telephone cables if not as "transmission
lines"? What do you suggest, depending on measurements only?
Measurements may tell us how a line works as we have connected it, but
it fails to give us any insight into how the line actually works. I
think the real problem here is that you are incapable of becoming any
wiser than you currently are.

The specific losses need to be considered according to application.

As Hyundai would say "Duh".


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[John Byrns]

In article ,
Eeyore wrote:

John Byrns wrote:

"Arny Krueger" wrote:

Yeah, I forgot propigation delay, but my sources say that the
propigation
coefficient of UTP 24 gauge is more like 70% than 25%.

That may well be correct, the approx. 25% figure I gave is for the
"standard telephone line" that Iain referred to on the first version of
his web page.

Actually, that's a *telegraph* line.

On what basis do you call it a "telegraph line" when Iain specifically
said it was a "standard telephone line"? The cable I found that most
closely matched Iain's description was a 19 gauge telephone toll cable,
which is the cable the 25% factor I quoted applies to. On the other
hand what if it is a "telegraph line", is there any real difference
between telephone cables and telegraph cables, I am fairly certain that
they both operate on the same principles? Furthermore it is my
understanding that "telegraph" cables have been utilized for the
transmission of audio signals, and that the Telegraph Company has leased
"telephone lines" from the Telephone Company to use for transmitting
telegraph signals.

It has no meaningful relationship
whatever
to modern audio circuits of any type. I suggest you forget it. This is the
trouble with using 1920's thinking.

How did you come to that conclusion, my telephone still depends on a
mile or two of cable to connect it to the RT, although admittedly beyond
that point the world becomes mostly fiber?

What is wrong with 1920s thinking? Those old guys weren't as dumb as
you would have us believe, and to the best of my knowledge the "1920s"
theory still holds, the laws of physics haven't yet been repealed.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Eeyore]

John Byrns wrote:

Eeyore wrote:
John Byrns wrote:
"Arny Krueger" wrote:

Yeah, I forgot propigation delay, but my sources say that the
propigation
coefficient of UTP 24 gauge is more like 70% than 25%.

That may well be correct, the approx. 25% figure I gave is for the
"standard telephone line" that Iain referred to on the first version of
his web page.

Actually, that's a *telegraph* line.

On what basis do you call it a "telegraph line" when Iain specifically
said it was a "standard telephone line"?

Because early long distance telephony used the very widely separated telegraph
line conctruction which does indeed produce a 600 ohm characteristic impedance.

Are you trying to suggest that this construction is STILL a "standard telephone
line" ?

Graham

[jim Gregory]

In the '60s, there were two other balanced comms impedances knocking around:
900 and 1,200 Ohms, I encountered them as Z options in test-gear catalogs.
Does anybody know what these were principally for?
Jim

"Eeyore" wrote in message
...


John Byrns wrote:

Eeyore wrote:
John Byrns wrote:
"Arny Krueger" wrote:

Yeah, I forgot propigation delay, but my sources say that the
propigation
coefficient of UTP 24 gauge is more like 70% than 25%.

That may well be correct, the approx. 25% figure I gave is for the
"standard telephone line" that Iain referred to on the first version
of
his web page.

Actually, that's a *telegraph* line.

On what basis do you call it a "telegraph line" when Iain specifically
said it was a "standard telephone line"?

Because early long distance telephony used the very widely separated
telegraph
line conctruction which does indeed produce a 600 ohm characteristic
impedance.

Are you trying to suggest that this construction is STILL a "standard
telephone
line" ?

Graham

[John Byrns]

In article ,
Eeyore wrote:

John Byrns wrote:

Eeyore wrote:
John Byrns wrote:
"Arny Krueger" wrote:

Yeah, I forgot propigation delay, but my sources say that the
propigation
coefficient of UTP 24 gauge is more like 70% than 25%.

That may well be correct, the approx. 25% figure I gave is for the
"standard telephone line" that Iain referred to on the first version of
his web page.

Actually, that's a *telegraph* line.

On what basis do you call it a "telegraph line" when Iain specifically
said it was a "standard telephone line"?

Because early long distance telephony used the very widely separated
telegraph
line conctruction which does indeed produce a 600 ohm characteristic
impedance.

If it is a line for telephony, then it is a telephone line even if it
shares its basic method of construction with telegraph lines, you are
making a silly semantic argument here. In any case if you look into the
details of the line mentioned on Iain's web page it becomes obvious that
the "standard telephone line" he was talking about was not an open wire
line such as you are talking about, but was a 19 gauge toll cable.

Are you trying to suggest that this construction is STILL a "standard
telephone
line" ?

I'm not sure if this is a trick question or not, as I expect most new
telephone cables, except for those used in the "last mile", are fiber
optic cables. But assuming we are talking about copper cables, yes I
expect that they still use the same basic construction, the main
difference being the use of new and different insulating materials.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Eeyore]

John Byrns wrote:

Eeyore wrote:
John Byrns wrote:
Eeyore wrote:
John Byrns wrote:
"Arny Krueger" wrote:

Yeah, I forgot propigation delay, but my sources say that the
propigation
coefficient of UTP 24 gauge is more like 70% than 25%.

That may well be correct, the approx. 25% figure I gave is for the
"standard telephone line" that Iain referred to on the first version of
his web page.

Actually, that's a *telegraph* line.

On what basis do you call it a "telegraph line" when Iain specifically
said it was a "standard telephone line"?

Because early long distance telephony used the very widely separated
telegraph line conctruction which does indeed produce a 600 ohm characteristic
impedance.

If it is a line for telephony, then it is a telephone line even if it
shares its basic method of construction with telegraph lines, you are
making a silly semantic argument here.

It's not semantic at all. It's fundamental.


In any case if you look into the
details of the line mentioned on Iain's web page it becomes obvious that
the "standard telephone line" he was talking about was not an open wire
line such as you are talking about, but was a 19 gauge toll cable.

What's a 'toll cable' outside the USA ?


Are you trying to suggest that this construction is STILL a "standard
telephone line" ?

I'm not sure if this is a trick question or not, as I expect most new
telephone cables, except for those used in the "last mile", are fiber
optic cables. But assuming we are talking about copper cables, yes I
expect that they still use the same basic construction, the main
difference being the use of new and different insulating materials.

NO THEY DO NOT USE THE SAME CONSTRUCTION !

Have you even the tiniest idea what a telegraph line looks like ?

Graham

[John Byrns]

In article ,
Eeyore wrote:

John Byrns wrote:

Eeyore wrote:
John Byrns wrote:
Eeyore wrote:
John Byrns wrote:
"Arny Krueger" wrote:

Yeah, I forgot propigation delay, but my sources say that the
propigation
coefficient of UTP 24 gauge is more like 70% than 25%.

That may well be correct, the approx. 25% figure I gave is for the
"standard telephone line" that Iain referred to on the first
version of
his web page.

Actually, that's a *telegraph* line.

On what basis do you call it a "telegraph line" when Iain specifically
said it was a "standard telephone line"?

Because early long distance telephony used the very widely separated
telegraph line conctruction which does indeed produce a 600 ohm
characteristic
impedance.

If it is a line for telephony, then it is a telephone line even if it
shares its basic method of construction with telegraph lines, you are
making a silly semantic argument here.

It's not semantic at all. It's fundamental.

You seem to want to walk both sides of the street here, either they are
the same, or they are fundamentally different, you can't have it both
ways.

In any case if you look into the
details of the line mentioned on Iain's web page it becomes obvious that
the "standard telephone line" he was talking about was not an open wire
line such as you are talking about, but was a 19 gauge toll cable.

What's a 'toll cable' outside the USA ?

Ya got me, you could tell us what they are called in the UK?

Are you trying to suggest that this construction is STILL a "standard
telephone line" ?

I'm not sure if this is a trick question or not, as I expect most new
telephone cables, except for those used in the "last mile", are fiber
optic cables. But assuming we are talking about copper cables, yes I
expect that they still use the same basic construction, the main
difference being the use of new and different insulating materials.

NO THEY DO NOT USE THE SAME CONSTRUCTION !

OK, I can believe the construction of telephone cables has changed over
the years, please describe the changes in the construction of telephone
cables over the years, excluding the obvious change in the materials
used for insulation?

Have you even the tiniest idea what a telegraph line looks like ?

Now it is back to open wire lines again, you really seem to have a thing
for open wire lines. I don't have the slightest clue how to distinguish
a telegraph line from a telephone line, I have always assumed that most
of the open wire lines I have seen are telephone lines. I do know that
the telephone company also used telegraphic signaling and transmitted
telegraph signals over their telephone lines. Also I believe that the
telegraph company here in the US leased some of their lines from the
telephone company, at least in the latter days. But back to what
telegraph lines look like, the only possible distinction I can think of
is that telegraph lines may use a different transposition scheme than
telephone lines, which use many different transposition schemes
depending on the type of carrier system employed with them. Of course
the telegraph lines we see in the old "Western movies" are only a single
line with an earth return.

So why don't you explain what a telegraph line actually looks like and
how to distinguish it from a telephone line?


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Eeyore]

John Byrns wrote:

Eeyore wrote:

Have you even the tiniest idea what a telegraph line looks like ?

Now it is back to open wire lines again, you really seem to have a thing
for open wire lines.

Because it's the only type of 'phone line' that has a characteristic impedance of
600 ohms. And *I* don't have a thing for 600 ohms, *YOU* do !


I don't have the slightest clue how to distinguish
a telegraph line from a telephone line

Speaks volumes about your ignorance.

Graham

[The Phantom]

On Sat, 25 Aug 2007 14:07:29 GMT, John Byrns wrote:

In article ,
Eeyore wrote:

John Byrns wrote:

Eeyore wrote:
John Byrns wrote:
Eeyore wrote:
John Byrns wrote:
"Arny Krueger" wrote:

Yeah, I forgot propigation delay, but my sources say that the
propigation
coefficient of UTP 24 gauge is more like 70% than 25%.

That may well be correct, the approx. 25% figure I gave is for the
"standard telephone line" that Iain referred to on the first
version of
his web page.

Actually, that's a *telegraph* line.

On what basis do you call it a "telegraph line" when Iain specifically
said it was a "standard telephone line"?

Because early long distance telephony used the very widely separated
telegraph line conctruction which does indeed produce a 600 ohm
characteristic
impedance.

If it is a line for telephony, then it is a telephone line even if it
shares its basic method of construction with telegraph lines, you are
making a silly semantic argument here.

It's not semantic at all. It's fundamental.

You seem to want to walk both sides of the street here, either they are
the same, or they are fundamentally different, you can't have it both
ways.

In any case if you look into the
details of the line mentioned on Iain's web page it becomes obvious that
the "standard telephone line" he was talking about was not an open wire
line such as you are talking about, but was a 19 gauge toll cable.

What's a 'toll cable' outside the USA ?

Ya got me, you could tell us what they are called in the UK?

Are you trying to suggest that this construction is STILL a "standard
telephone line" ?

I'm not sure if this is a trick question or not, as I expect most new
telephone cables, except for those used in the "last mile", are fiber
optic cables. But assuming we are talking about copper cables, yes I
expect that they still use the same basic construction, the main
difference being the use of new and different insulating materials.

NO THEY DO NOT USE THE SAME CONSTRUCTION !

OK, I can believe the construction of telephone cables has changed over
the years, please describe the changes in the construction of telephone
cables over the years, excluding the obvious change in the materials
used for insulation?

Have you even the tiniest idea what a telegraph line looks like ?

Now it is back to open wire lines again, you really seem to have a thing
for open wire lines. I don't have the slightest clue how to distinguish
a telegraph line from a telephone line, I have always assumed that most
of the open wire lines I have seen are telephone lines. I do know that
the telephone company also used telegraphic signaling and transmitted
telegraph signals over their telephone lines. Also I believe that the
telegraph company here in the US leased some of their lines from the
telephone company, at least in the latter days. But back to what
telegraph lines look like, the only possible distinction I can think of
is that telegraph lines may use a different transposition scheme than
telephone lines, which use many different transposition schemes
depending on the type of carrier system employed with them. Of course
the telegraph lines we see in the old "Western movies" are only a single
line with an earth return.

So why don't you explain what a telegraph line actually looks like and
how to distinguish it from a telephone line?

What he's getting at and won't tell you even when you ask is that the
vintage telegraph line was a single wire with earth return.

http://home.iprimus.com.au/oseagram/morse.html



Regards,

John Byrns